Buggy code:
public abstract class WizardPreferencesPage extends WizardPage implements Listener , IOverwriteQuery { protected Combo destinationNameField ; private Button destinationBrowseButton ; private Button overwriteExistingFilesCheckbox ; protected Table transfersTable ; protected Text text ; private Composite buttonComposite ; private Button allButton ; protected Button chooseImportsButton ; private Group group ; private static final String STORE_DESTINATION_NAMES_ID = "WizardPreferencesExportPage1.STORE_DESTINATION_NAMES_ID" ; private static final String STORE_OVERWRITE_EXISTING_FILES_ID = "WizardPreferencesExportPage1.STORE_OVERWRITE_EXISTING_FILES_ID" ; private static final String TRANSFER_ALL_PREFERENCES_ID = "WizardPreferencesExportPage1.EXPORT_ALL_PREFERENCES_ID" ; private Hashtable imageTable ; private PreferenceTransferElement [ ] transfers ; private String currentMessage ; private static final String STORE_DESTINATION_ID = null ; protected static final int COMBO_HISTORY_LENGTH = 5 ; protected WizardPreferencesPage ( String pageName ) { } protected Button createButton ( Composite parent , int id , String label , boolean defaultButton ) { } protected void addDestinationItem ( String value ) { } public void createControl ( Composite parent ) { initializeDialogUnits ( parent ) ; Font wizardFont = parent . getFont ( ) ; Composite composite = new Composite ( parent , SWT . NULL ) ; composite . setLayout ( new GridLayout ( ) ) ; composite . setLayoutData ( new GridData ( ( ( GridData . VERTICAL_ALIGN_FILL ) | ( GridData . HORIZONTAL_ALIGN_FILL ) ) ) ) ; composite . setFont ( wizardFont ) ; createTransferArea ( composite ) ; restoreWidgetValues ( ) ; <START_BUG> if ( ! ( validDestination ( ) ) ) <END_BUG> setPageComplete ( false ) ; setPreferenceTransfers ( ) ; setControl ( composite ) ; giveFocusToDestination ( ) ; } protected abstract void createTransferArea ( Composite composite ) { } protected boolean validateDestinationGroup ( ) { } protected abstract String getInvalidDestinationMessage ( ) { } private String getNoOptionsMessage ( ) { } protected boolean validDestination ( ) { } protected void setPreferenceTransfers ( ) { } protected PreferenceTransferElement [ ] getTransfers ( ) { } private void createItem ( PreferenceTransferElement element , Table table ) { } private Hashtable getImageTable ( ) { } protected void createTransfersList ( Composite composite ) { } protected abstract String getChooseButtonText ( ) { } protected abstract String getAllButtonText ( ) { } private void addSelectionButtons ( Composite composite ) { } protected void setAllChecked ( boolean bool ) { } protected void createDestinationGroup ( Composite parent ) { } protected void createOptionsGroup ( Composite parent ) { } protected boolean ensureDirectoryExists ( File directory ) { } protected boolean queryYesNoQuestion ( String message ) { } protected boolean ensureTargetIsValid ( File file ) { } protected void saveWidgetValues ( ) { } public boolean finish ( ) { } protected IPreferenceFilter [ ] getFilters ( ) { } protected PreferenceTransferElement [ ] getPreferenceTransferElements ( ) { } protected abstract boolean transfer ( IPreferenceFilter [ ] transfers ) { } public void setPageComplete ( ) { } protected boolean determinePageCompletion ( ) { } protected boolean validateOptionsGroup ( ) { } protected boolean validateSourceGroup ( ) { } protected abstract String getDestinationLabel ( ) { } protected String getDestinationValue ( ) { } protected void giveFocusToDestination ( ) { } protected void handleDestinationBrowseButtonPressed ( ) { } protected abstract String getFileDialogTitle ( ) { } protected abstract int getFileDialogStyle ( ) { } public void handleEvent ( Event e ) { } protected void updatePageCompletion ( ) { } protected void internalSaveWidgetValues ( ) { } protected String [ ] addToHistory ( String [ ] history , String newEntry ) { } protected void addToHistory ( List history , String newEntry ) { } protected void restoreWidgetValues ( ) { } private boolean getOverwriteExisting ( ) { } private boolean getTransferAll ( ) { } protected void setDestinationValue ( String value ) { } public void dispose ( ) { } protected boolean allowNewContainerName ( ) { } public String queryOverwrite ( String pathString ) { } }

Fix:
if ( ! ( ( ( validDestination ( ) ) && ( validateOptionsGroup ( ) ) ) && ( validateSourceGroup ( ) ) ) )